Broodmare Removal From Fescue Helps Protect Owner Investment
By Donald Stotts
STILLWATER - Decreasing the consumption of endophyte-infected fescue through supplementation with grain may benefit growing horses, but the same recommendation cannot be made for broodmares.
Supplementation does not ensure a reduction of endophyte-related problems in pregnant broodmares, said Dave Freeman, Oklahoma State University Extension equine specialist.
"In one study involving mares in late gestation, mortality was 66 percent for those receiving grain supplementation and 50 percent for non-supplemented mares when both groups were fed endophyte-infected hay," he said.
Freeman recommends that mares not receiving the drug domperidone be removed from fescue pastures six weeks to three months before the expected foaling date.
Domperidone is currently under field investigation by veterinarians to determine its effectiveness and best schedule of treatments. Mares that receive daily doses of domperidone several days before foaling do not appear to develop symptoms of fescue toxicosis when consuming endophyte-infected fescue.
Freeman said researchers who developed the drug hope to received U.S. Food and Drug Administration approval for widespread use in the near future.
Fescue-related problems in broodmares have been associated with gestation, foaling and milk production.
"Mares that consume endophyte-infected fescue can have prolonged gestation lengths in excess of the normal 335 to 345 days, probably because of interference with normal hormonal activity," Freeman said.
Foaling mares that consume endophyte-infected fescue also have an increased incidence of dystocia (foaling difficulty). Many equine researchers believe this is caused by an inadequate preparation of the reproductive tract, prolonged gestation and fetal malpresentation.
"Mare and foal death can result from these incidences of dystocia," Freeman said.
In addition, mares that have been consuming endophyte-infected fescue frequently have a complete absence of milk production (agalactia).
Freeman said the agalactia probably is caused by decreased production of the hormone prolactin.
"Agalactia appears to be the most consistently observed problem in mares consuming endophyte-infected fescue," he said.
The recommended time for removal of mares approaching parturition from endophyte-infected fescue varies from veterinarian to veterinarian, or from equine specialist to equine specialist.
Freeman said the few studies that have been conducted suggest rapid recovery of mares that are removed from endophyte-infected pastures. There are indications that problems can be avoided by removing mares as late as 30 days before foaling.
"However, since the dual purposes of a breeding program are to produce a live, healthy foal and a successfully rebred mare, play it safe, protect your investment and remove broodmares from fescue pastures at least six weeks prior to the expected foaling date," Freeman said.
Fescue is the most persistent, best adapted, cool season perennial forage grown in eastern Oklahoma. The plant also grows further west, but does not produce well on sites prone to drought or in deep sands.
There is no known chemical or non-chemical treatments that will remove the endophyte Neotyphodium from infected fescue plants. Eradication of pre-existing fescue from pasture land is difficult, slow and costly.
"Those thinking about fescue eradication programs should contact their local Oklahoma Cooperative Extension Service office to determine feasibility, likely cost and potential effectiveness," Freeman said.
For more information on domperidone, veterinarians can write to Dr. Dee Cross, Animal Science, Dairy and Veterinary Sciences Department, P.O. Box 340361, Clemson University, Clemson, SC 29634-0361.
We would like to take this opportunity to thank Oklahoma State University for allowing us to provide you with this information.
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